Island County, in Washington, sits in USDA hardiness zone 8b — a zone band wide enough that plant choice, not possibility, is the interesting question.
Among the crops suited to this profile: cabbage, fig, california poppy, and collard greens. The site-level story — soil, sun, drainage — decides the rest.
Island County lies within the Puget Sound Lowlands and the Pacific Northwest — a regional growing area with its own character.
Grounded in USDA PHZM 2023 · Growable Ground suitability scoring · NOAA 1991–2020 Climate Normals
Island County holds more than one microclimate.
Soils and elevations shift across Island County, so your frost dates and drainage aren't the county average. Enter your address and we'll score 1,086 plants against your land's actual soil, sun, and frost.
We read public map data around Island County — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
Island County — the short answer
Island County, Washington: USDA zone 8b, about 292 days between hard freezes, across 134K acres.
- USDA zone
- 8b
- USDA PHZM 2023
- Last hard freeze (28°F)
- Feb 8
- NOAA 1991–2020 Climate Normals, 28°F
- First hard freeze (28°F)
- Nov 27
- NOAA 1991–2020 Climate Normals, 28°F
- Days between freezes
- ~292
- NOAA 1991–2020 Climate Normals, 28°F
- County area
- 134K acres
- US Census TIGER/Line 2025
Every figure names the dataset it came from. Hard-freeze dates are county 28°F normals: light frosts run a few weeks past them, and tender transplants usually wait 2–3 weeks after the last hard freeze.
Hardiness Zone Range
Zone 8b is Island County's average, not your lot's — a low corner or a tree line moves it. Against Island County's 292-day season, see what your own ground reads.
Heat in Island County
Across a year, Island County accumulates about 1,121 growing degree days above 50°F, about 592 fewer than the middle Washington county — ahead of 6 of Washington’s 39 counties. Degree days are the heat a crop actually gets to work with — more of them is more room to ripen a long-season crop before the freeze closes the window.
Grounded in PRISM Climate Group, Oregon State University — 1991–2020 monthly normals
Soil in Island County
Across Island County, the ground is predominantly Inceptisols, where Indianola, Zylstra, and Uselessbay are the most extensive named soil series. The soil is generally somewhat excessively drained with a sandy loam surface. Topsoil pH runs about 5.4–6.2, moderately acidic. Rainfall drains through hydrologic group A soils.
Soil order
Inceptisols
Drainage
Somewhat excessively drained
Prime farmland
5%
Hydric soils
10%
Soil still varies lot by lot — soil types explained.
How the ground varies across Island County
The USDA soil survey maps 35% of Island County as somewhat excessively drained — but another 60% drains differently: 29% moderately well drained, 17% somewhat poorly drained.
Indianola is the most extensive named soil at 13% of mapped acres, then Zylstra (9%) and Uselessbay (8%).
Which of them your own lot sits on is a parcel question, not a county one. Check your address for the survey at your boundary.
What this means for growing in Island County
Each reading below is measured for Island County itself — here is what it means for a garden here, and the move an experienced grower makes about it.
Drainage
MeasuredThe dominant soils across Island County are somewhat excessively drained, in hydrologic group A — ground that drains quickly.
The upside is soil you can work early in spring and roots that never drown; the cost is that fast-draining ground dries out fast and leaches nutrients away before plants can use them.
Work in compost and mulch to hold moisture and feed, and water more often in short doses than deep and rarely.
USDA NRCS SSURGO
Surface pH
MeasuredTopsoil across Island County runs about pH 5.4–6.2, on the acidic side.
Blueberries, potatoes, and rhododendrons thrive in it, but most vegetables start locking out nutrients below about pH 6.0 and grow pale and stunted no matter how much you feed them.
A measured lime application raises pH for the crops that need it — but test first, because the right rate depends on your own soil, not the county average.
USDA NRCS SSURGO
Season length
MeasuredIsland County runs about 292 days between hard freezes — close to year-round growing.
Frost is rarely the limit here; winter plantings are as real as summer ones, and the harder question is which crops shrug off the summer heat.
Grow cool-season crops through the mild winter, and choose heat-tolerant varieties for the summer beds.
NOAA 1991–2020 Climate Normals
Winter hardiness
MeasuredIsland County sits in USDA hardiness zone 8b.
The zone sets which perennials, shrubs, and fruit trees live through an average winter here — a plant rated for a colder zone is a safe bet, one rated warmer needs winter protection or gets treated as an annual.
Match perennials and fruit to the zone before you buy, so nothing you plant is a gamble against the cold.
USDA PHZM 2023
The kind of country Island County is in
Island County sits in the Puget Lowland — EPA Level III, inside the wider Marine West Coast Forest. One consistent ecological setting across the whole county.
What Grows in Island County
We scored all 1,086 plants against Island County's own USDA zone 8b and its own 292-day season between hard freezes, using the same matching engine that runs a full parcel report. These cleared both. Sun, soil pH and drainage vary lot by lot — those are the parcel questions below. Each card opens that plant's Washington profile.
Is it too late to plant in Island County?
Too late for some crops, right on time for others — a growing season is a sequence, not a deadline. Cool-season crops can go in from around Jan 11; tender transplants wait until two to three weeks after the last 28°F hard freeze, which lands near Feb 8 (NOAA 1991–2020 climate normals); and from midsummer, planting counts back from the first fall freeze around Nov 27 — long-season crops need about 90 days of runway, quick greens only 30. And with a calendar this mild, the honest answer is that planting barely stops — winter opens seasons colder regions never see.
What gets applied to farmland in Island County
USGS estimates 5,339 lb of Glyphosate on Island County farmland in 2019, its largest by weight, ahead of Bromoxynil (852 lb) and 2,4-d (443 lb).
Farmland across the whole county, not any one lot. Check your address for the site-by-site record.
Safe to Grow Here?
What the federal record shows across Island County — and how to grow with it.
We checked the federal record across Island County — 197 documented sites across 7 of the 9 source types we track.
The most significant on record: 4 Superfund sites. Sites tracked in EPA's Superfund program — from assessment-stage CERCLIS entries to confirmed National Priorities List cleanup sites.
There's a meaningful federal record across Island County — worth a look before you plant food, not a reason to hold back from growing. Proximity to a documented site is information, not a diagnosis of any one yard. A soil test before new food beds is the sensible precaution here, and the map shows exactly which sites sit where, so you can see what's actually near you.
Sources: EPA, USGS — 1.8M documented sites tracked nationwide across 9 federal source types.
What's on the federal record near Island County
Closest first, across Island County. Listing isn't leaking, and distance isn't exposure.
- FORT CASEY MILITARY RESERVATION - FUDS SITESuperfund · 0.5 mi
- FORT CASEY STATE PARKUnderground Storage Tanks · 0.8 mi
- SEATTLE PACIFIC UNIV AUTO SHOPBrownfields · 0.8 mi
- SEATTLE PACIFIC UNIVERSITY CASEY CONFERENCE CTRUnderground Storage Tanks · 0.8 mi
- 31N/01E-14B02Nitrate · 1.7 mi
- COUPEVILLE TOWN OFPFAS · 2.8 mi
- ENGLE FARMSUnderground Storage Tanks · 3.2 mi
- COUPEVILLE ROAD SHOPUnderground Storage Tanks · 3.3 mi
- COUPEVILLE SCHOOL DISTRICT 204Underground Storage Tanks · 3.4 mi
- SHELL MAIN & TERRY COUPEVILLEUnderground Storage Tanks · 3.4 mi
- ISLAND MARINE & SPORTSUnderground Storage Tanks · 3.4 mi
- PRAIRIE CENTER RED APPLE MARKETUnderground Storage Tanks · 3.5 mi
6 more sites are on the record inside the same radius. See them on the map
Measured from Island County's center, not your beds. Run your own address for what's upwind of you specifically.
Environmental Intelligence
The counts behind that headline — every source type on the record near Island County.
Sources Checked
across Island County
Severity Distribution
across Island County
Highest-Severity Sites
A note from Gnorman
What an experienced grower watches for around here
In and around Island County, two things run higher than the national average across Island County — PFAS (6 sites) and Superfund (4 sites). Knowing it is half the work — and it's nothing a thoughtful grower can't plan for.
PFAS: PFAS (per- and polyfluoroalkyl substances) are called "forever chemicals" because they do not biodegrade.
Superfund: Superfund sites represent the most severe contamination in the federal system.
Test irrigation water source — this is the primary pathway for PFAS to reach garden crops.
Commission professional soil testing before any food production (test for heavy metals, VOCs, and SVOCs).
Check your specific parcel in Island County
Get exact proximity distances to contamination sources for your specific parcel — plus soil, sun, drainage, and 1,086 plant recommendations.
25+ data sources read at your address, not the Island County average
Your land is one point inside Island County
Everything above resolves to Island County as a whole — one PHZM band and one county frost record, read across 134K acres. Your parcel is one point inside that footprint. Slope, tree cover, a low spot that pools cold air, and what is in the soil are all resolved at the address, and none of them are visible at county scale. That is the honest boundary of this page, and the reason the next step is a reading of your own ground rather than a better county average.
Your Lot vs the Island County Average
Island County Average
- ●USDA Zones 8b, averaged across Island County
- ●One soil character for all of Island County
- ●Frost dates read at Island County's scale: Feb 8 to Nov 27
YOUR Parcel
- ✓Your exact zone, not Island County's 8b
- ✓Your SSURGO soil type & pH
- ✓Your sun exposure, cast in 3D
See MY Growing Report
Read your parcel in Island County
Pull a site-specific report for your exact address in Island County, Washington — soil, sun, drainage, frost risk, and scored plant recommendations.
Three things about your lot that Island County averages can't show:
We read public map data around Island County — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources read at your address, not the Island County average
How we know this about Island County
The datasets: hardiness from the USDA ARS Plant Hardiness Zone Map 2023, read at county grain; hard-freeze dates from NOAA 1991–2020 28°F normals at this county’s own record where one resolves, and the labelled statewide window where none does; soils from the USDA NRCS SSURGO survey, area-weighted across the county’s own map units; boundaries and acreage from US Census TIGER/Line 2025; the contamination and pesticide records from the federal sources named in their beats above. Where Island County carries no record of its own, the figure is inherited and labelled — the resolution ledger below names each.
Common questions about Island County
When does frost risk typically end in Island County?
The last hard freeze (28°F) in Island County typically lands around Feb 8, per NOAA 1991–2020 climate normals — earlier than the light-frost dates most charts quote. That marks the hard freeze, not the last light frost — lighter frosts keep biting past it, which is why tender transplants here wait until about Mar 1.
How long is the growing season in Island County?
Measured between 28°F hard freezes, Island County sees about 292 frost-free days — roughly Feb 8 through Nov 27, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Mar 1 to Nov 13, about 257 days.
Is the soil safe to grow vegetables in Island County?
The federal record around Island County is a meaningful one — 197 documented sites, mostly Underground Storage Tanks entries (119), the nearest Superfund record about 0.5 miles out — so a soil test before new food beds is a sensible precaution here, not a reason to hold back from growing. Remember that proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what sits where.
Everything above is measured at Island County's scale — its 8b band and its 292-day season. Your yard writes its own version of Island County's numbers: we read soil, sun, drainage and frost at your exact address. Try it for 14 days — no card required.
Will It Grow Here?
Zone fit is the first question — each answer below reads Washington's frost window, season length, and soil profile against the plant's real requirements.
What this page reads at Island County’s own scale
8 of the readings below were taken at Island County's own scale — its own ~292-day span between 28°F freezes, the 3 most extensive soil series mapped here and 197 documented sites inside its boundary; one is borrowed from a wider read, named and linked below.
Measured here
- Island County's own USDA hardiness band, zones 8bUSDA PHZM 2023
- Island County's own 28°F hard-freeze dates and its ~292-day span between themNOAA 1991–2020 Climate Normals
- The soil order, drainage, surface pH, and the 3 most extensive named soil series mapped in Island CountyUSDA NRCS SSURGO
- 197 documented contamination sites inside the county boundary, distance-sorted from its center — the closest Superfund record about 0.5 miles outFederal environmental registers
- Island County's boundary and the 133,567 acres inside itUS Census TIGER/Line 2025
- Which of 1,086 plants clear zones 8b and a ~292-day seasonGrowable Ground crop-matching engine
- Island County sitting wholly inside the Puget LowlandUS EPA Level III Ecoregions
- Which agricultural compounds go onto Island County farmland, and roughly how muchUSGS NAWQA EPest county estimates
Inherited from a wider read
- The growing challenges every Washington grower plans around — written at state scale, so they stay on the state guidefrom Washington
What this page can’t tell you
- How the season shifts across Island County — the ~292 days above is one reading at its centre; the 12 towns below each carry their owntowns in this county →
- The soil pH, drainage, sun hours, and frost pockets on any one lot among Island County's 133,567 acreswhy one lot differs from the next →
- Which of those 197 documented sites actually reaches your soil — that needs your address, the wind, and the groundwater directionhow we read the record →
- Where cold air settles, which slopes face the sun, and which way the wind runs on your own ground — none of it survives being averaged over Island Countyread your own land →